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Cage‐like metal–organic frameworks (MOFs) are promising for hexane isomer separation, but their aperture sizes are difficult to control precisely. Herein, a molecular valve strategy is proposed to fine‐tune the aperture of cage‐like MOFs, thereby enhancing their separation performance for hexane isomers. Three novel isostructural cage‐like MOFs, namely Cu‐MO4‐TPA, are synthesized using different oxometallate anions (MO42−, M = Cr, Mo, and W) and the ligand tri(pyridin‐4‐yl)amine (TPA). The different oxometallate anions induce varying degrees of twisting in the TPA ligand, leading to sub‐angstrom tuning in the aperture size of the MOFs. The materials can separate hexane isomers based on their degree of branching, with the smallest aperture material (Cu‐MoO4‐TPA) showing molecular sieving of di‐branched isomers. Adsorption isotherms, kinetic, and breakthrough measurements, Monte Carlo, and density functional theory calculations confirm the aperture size differences result in superior separation of hexane isomers by molecular sieving on Cu‐MoO4‐TPA. The results demonstrate the effectiveness of molecular valve strategy for fine‐tuning MOF aperture size for selective separation applications. [ABSTRACT FROM AUTHOR]

The designability and ultrahigh stability of zirconium–organic frameworks make them attractive adsorbents for noble gases xenon (Xe) and krypton (Kr), but their Xe/Kr separation performance needs to be further enhanced. In this study, we rationally control the topology and porosity of zirconium–fumarate frameworks by simply changing the synthesis conditions, and successfully construct an adsorbent (named as MIP‐203‐F) with one‐dimensional pore instead of the original cage‐like fcu metal–organic framework MOF‐801. The Xe/Kr separation performance of MIP‐203‐F is thoroughly evaluated by isotherm measurements and breakthrough experiments, while the adsorption mechanism is elucidated in detail by Monte Carlo and density functional theory calculations. Due to the uniform pore with suitable size and abundant polarization groups, MIP‐203‐F can differentially polarize and recognize atomic Xe/Kr gases, and establishes a new record among zirconium–organic frameworks for the capture and separation of Xe/Kr. [ABSTRACT FROM AUTHOR]

Adsorbents executing molecular sieving mechanisms for the efficient separation of n‐hexane (C6) alkane isomers require delicate pore size control, but afford unsatisfactory single‐component separations according to their branch degrees. Herein, we report a novel oxygenate‐pillared microporous adsorbent, MoOFOUR‐Co‐tpb, ([Co(tpb)2MoO4], tpb = 1,2,4,5‐tetra(pyridin‐4‐yl) benzene), with three gourd‐shaped channels for dual pore‐size sieving of C6 isomers. In particular, MoOFOUR‐Co‐tpb excludes 2,2‐dimethylbutane, while 3‐methylpentane (3MP) can enter one channel showing a high uptake of 82.6 mg g−1, contrasting to the n‐hexane (nHEX) adsorption by two channels (136 mg g−1). This dual pore‐size control strategy renders a record high equilibrium–kinetic combined selectivity for nHEX/3MP (30.2). Moreover, three‐ and five‐component breakthrough experiments confirm the practical separation performances and cycling stability. Multiple theoretical simulations reveal the separation mechanism and adsorption sites. [ABSTRACT FROM AUTHOR]

Removal of the CO 2 impurities from C 2 H 2 /CO 2 mixtures is an essential process to produce high-purity C 2 H 2 . Fabricating an adsorbent capable of discriminating these species, which have close kinetic diameters, is critical for developing advanced adsorption processes. Herein, we demonstrate a strategy to exploit the tunability of interlayer and intralayer spaces of two-dimensional (2D) layered metal-organic frameworks to achieve high performance for C 2 H 2 /CO 2 separation. This indicates that interlayer symmetrical control can achieve more efficient packing of C 2 H 2 into Ni(4-DPDS) 2 CrO 4 , with a high C 2 H 2 capacity of 45.7 cm 3 ·g -1 at 0.01 bar and a selectivity of 67.7 (298 K, 1 bar), which strikes a good balance between working capacity and separation selectivity compared to other isostructural Ni(4-DPDS) 2 MO 4 (M = Mo, W). Crystallographic studies and DFT-D calculations reveal that such a C 2 H 2 -selective adsorbent possesses strong binding interactions due to the tailored pore confinement provided by the angular anions and rich electronic environment. Experimental breakthrough results comprehensively demonstrate the efficient C 2 H 2 /CO 2 separation performance of this unique material.